Abstract: The mammalian innate immune system provides non-specific and immediate responses to microbial invasion, constituting a primitive defense mechanism that modulates host/pathogen interactions and prevents the onset of disease. Ribosomally-synthesized antimicrobial peptides are ubiquitous components of the innate immune response, protecting mucosal surfaces from bacterial invasion. Following release into the extracellular space, many antimicrobial peptides exert non-specific antibacterial action by penetrating and disrupting the outer membranes of bacterial cells. We believe that additional and unrecognized roles for these peptides exist and we are motivated to elucidate how antimicrobial peptides contribute to host physiology prior to their extracellular release. Based on structures and cellular localizations, we hypothesize that select antimicrobial peptides are key players in regulating zinc homeostasis. A central goal of this proposal is to identify and investigate synergies between ribosomal peptide-based antibiotics and zinc at the molecular and physiological levels. We present a multifaceted experimental program that draws upon inorganic chemistry and cell biology to (i) address interactions between peptides, metal ions, other biomolecules and putative cellular targets, and (ii) decipher the downstream physiological consequences for the host and microbial pathogens. This initiative is significant and innovative because it provides a completely new framework for considering antimicrobial peptides and metal ion stores, that latter of which are essential but oftentimes overlooked in the contexts of the immune response and antibacterial therapeutic development. These studies will enhance our understanding of fundamental mechanisms that underlie metal ion physiology and the host/pathogen interaction and thereby impact the fields of biomedicine, medicinal chemistry, and public health. ) Public Health Relevance: This research initiative lies at the chemistry/biology/medicine interface, addresses fundamental mechanisms of human innate immunity and mucosal defense, and seeks to establish unrecognized connections between antimicrobial peptides and zinc biology. The outcomes of the proposed investigations will afford important new insights into the mammalian immune response, the host/pathogen interaction, and metal ion physiology. This basic research is relevant to public health;elucidating the chemistry and biology that underlies physiology is essential for improving our understanding of human health and combating disease.